Elevated concentrations of synthetic fluorinated glucocorticoid analogs transiently increase the intracellular exchangeable calcium in cultured bone cells

Abstract

Summary. This study investigated the influence of various glucocorticoids on the transport and accumulation of Ca 2+ in cultured bone cells. For measuring changes in the amount of intracellular exchangeable Ca 2+, cultures were initially preincubated with 4~Ca for 48 h thereby achieving a steady state. Triamcinolone acetonide induced a transient increase in the cells' content of exchangeable Ca2+--an effect that lasted for 5 h and was followed by a pronounced decrease as noted at 24 h. A similar increase was observed with dexamethasone, whereas hydrocortisone and corticosterone led to a less significant effect. No significant changes took place with the use of deoxycorticosterone, progesterone, and estradiol. The effect of triamcinolone on the cellular content of exchangeable Ca 2+ was completely blocked by both cycloheximide and puromycin when added shortly after the addition of the corticosteroid to the culture system. In order to determine the effect of steroid hormones on the initial rate of Ca 2+ influx into cultured cells, cultures were first preincubated with the various hormones and thereafter 45Ca was added. Only fluorinated glucocorticoid analogs such as triamcinolone acetonide and dexamethasone induced significant rises in the initial rate of Ca 2+ influx.Ultrastructural examinations showed that in 5-day-old control cultures osteoblast-like cells show multiple aggregates of calcium pyroantimonate along their plasma membrane. In contrast, similar cells cultured in the presence of triamcinolone (10-TM) for 3 h lacked such precipitates along their plasma membrane but instead contained aggregates of calcium pyroantimonate within enlarged mitochondria. Bone cells that were incubated with Send offprint requests to Dr. Michael Silbermann at the above address.triamcinolone for a longer period of time (24 h) exhibited hypertrophied mitochondria that were devoid of such calcium precipitates. Hence this study indicates that potent synthetic analogs of glucocorticoids affect: (a) the rate of calcium influx into bone cells, (b) the intracellular concentration of calcium, and (c) the distribution of calcium within these cells.

Receptor-mediated glucocorticoid inhibition of cell proliferation in mouse growth cartilage in vitro

“…One such factor is the concentration of calcium ions. Triamcinolone has been shown to increase both in vivo and in vitro the calcium concentration within chondrocytes as well as within bone cells (Eilam et al 1982;Maor & Silbermann, in press; Lewinson & Silbermann, in press). Altera¬ tion in the intracellular levels of cAMP have also been found to alter the rate of cartilage cell prolife¬ ration, and we are currently investigating the pos¬ sibility of cAMP involvement in corticosteroid-induced depression of DNA synthesis in cartilage The effect of cortexolone on the inhibitory effect of triamcinolone acetonide on DNA synthesis in cartilage in vitro.…”

In vitro precocious accumulation of calcium and matrix vesicles formation in young cartilage cells: Specific effects of corticosteroids

“…The induction of matrix vesicles by glucocorticoids could be the result of the accretion of cellular calcium as has been shown in both bone cells culture [15] and cartilage in vitro [16]. It has been recently suggested by Wuthier [17] that concentration of calcium complexes along the inner aspect of cell membranes might lead to membranous changes and subsequently to the elaboration of matrix vesicles, which are then shedded off into the extracellular matrix.…”